the science of murder
by ShadowsTakeAll
Summary: When a new serial killer begins terrorizing Boston, it's up to BPD to put a stop to it. But the killer's MO hits too close to home, and the case takes an even more personal turn when one of their own confesses a deadly secret, causing the investigation itself to be called into question. Have they found the killer, or is there more to the story?
1. Chapter 1

**Hi there, R &I fans, and welcome to my new story. Some of you may have read my previous story, _ignoratio elenchi,_ while others may be entirely unfamiliar with my writing. Either way, welcome, and I'm happy you decided to check out this fic. Things you need to know: it's set after the first couple of seasons (before certain character deaths), focuses a lot on the aftermath of what happened with Hoyt, and is heavy on the Rizzles feels (friendship-wise, not really romantic). That's probably all you need to know for now, but feel free to review/PM me with any questions. Here you go.**

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 _"Beware; for I am fearless, and therefore powerful."  
_ _― Mary Shelley, Frankenstein_

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"Well?"

The word was accompanied by an action – an index finger tapping on a paper coffee cup; something innocuous enough but with a clear meaning behind it. The hand clasped around the cup, but that action too held meaning, signalling barely hidden impatience. The woman holding the coffee had been called into work early, the call having actually roused her from her bed, where she had been attempting to sleep off last night's activities – and her appearance was suffering as a result.

She glanced down at the woman she was talking to, who was crouching over a dead body. Another murder, another crime scene. Except this wasn't just another – this could be something so much worse.

"And by the way," the woman holding the coffee said, "how is it that you stayed out later than I did last night but you look like you're ready to step onto a runway?"

The woman on the ground looked up, her puzzled expression softening into a smile. "I've told you before, Jane, your beauty regime isn't sufficient to negate the effects of -"

"Yes, thank you, Maura," Jane cut in, rolling her eyes good-naturedly. Maura _had_ told her that before, countless times, and Jane was no more likely to listen to her this time than she had any other. It's not like she had anyone who would actually pay attention to her appearance anyway; unlike Maura, who seemed to be fending off new suitors on a weekly basis. Not that Jane was jealous, of course. She was just concerned, given how well Maura's love life had gone in the past.

They fell silent while Maura continued examining the body. Jane knew better than to interrupt her, so she turned her attention to the other people in her team. Korsak and Frost were interviewing some of the neighbours, but they didn't seem hopeful. Somehow this woman had been murdered in the middle of a suburban street and nobody had seen a thing. She turned her gaze to Frankie, who was combing the area with some of the uniforms, searching for any material evidence. But if Jane was right about this, there wouldn't be any evidence to find.

"The MO is consistent with the other two," Maura said finally. She gestured for Jane to kneel down beside her for a better look, and once the detective had complied she went on, "Single laceration to the throat. Same depth as the first two victims. And see here?" She used one gloved finger to gently nudge open the victim's blouse, revealing the letter _M_ carved into her chest.

"It's the same," Jane said. She pressed a fist against her mouth, disgusted. Involuntarily her eyes fell onto the victim's hands. Because of the way the woman was lying Jane couldn't see the entirety of her hands, but she could see enough. Through each palm would be a single wound, just about the right size for a scalpel. The same as on Jane's hands. "The same guy killed all three of them."

"The manner of death is the same," Maura said cautiously, looking almost visibly hurt by the way Jane was making her assertions. "That's all I'm willing to say. I won't know everything until -"

"- you get back to the lab and do a full autopsy," Jane finished for her, well aware of the doctor's system. "But – and please don't dissect me just for suggesting it – do you think it's _possible_ that this woman was killed by the same person who killed the first two victims?"

Maura stood up and Jane followed her lead, and for a moment the doctor surveyed her carefully. There was something off about her, Jane realized, although she couldn't pinpoint what it was. Maybe the late night had affected her more than she let on. "It's possible," she conceded, but before Jane could so much as offer her a self-satisfied smile, she continued, "but it's also possible that this is a copycat killer, or an isolated incident, or -"

"Jane?"

She turned at the sound of her name and was relieved to see Frost approaching her. "Look, something relevant," she said, cutting off Maura. She turned to the other detective, who was flipping his notebook closed as he reached her. "Got anything, Frost?"

He shook his head, turning to glance up the street, where Korsak was talking to a couple of elderly women who, judging by their expressions and gestures, were probably trying to give him fashion advice. "Nobody saw a thing," he reported, turning back to Jane. "Which is a little hard to believe. This is a busy street, even at night. Why didn't anyone see anything?" He sighed, and then addressed Maura. "You got a time of death?"

The doctor's eyes widened and she started to speak, but Jane spoke first. "We're not looking for an exact-to-the-second figure, Maura," she said. "Just give us something to work with."

Relaxing slightly now that she knew they weren't actually asking her to guess, Maura looked down at the body, thought for a minute, and then said, "I'd say the murder occurred between six to eight hours ago."

Jane made a quick calculation. "So between twelve thirty and two thirty," she said, and Maura shrugged to indicate that she couldn't be any more specific. "All right." Jane looked up and down the street again. It seemed like everyone was packing up. Frankie waved at her and then spread his hands wide, silently telling her that he hadn't found anything useful, and Korsak finally disengaged himself from the elderly ladies and started coming over to Jane, Maura, and Frost.

"I think we've done everything we can do here," he said when he reached them, and Frost – who hadn't looked at the victim's body since he'd arrived – looked relieved at the thought of leaving. Jane and Maura shared a gently teasing look, which Frost pretended not to notice, and then Korsak cleared his throat. "Let's get everything back to the labs and see what we can find."

Although it was something she didn't like to talk about, Maura felt much more comfortable in the morgue than up in the bullpen with the others. Down here she was in control; she knew every piece of equipment, every scrap of evidence, every crack in the ceiling. She was perfectly at home among the bodies and the blood specimens and the scalpels, and part of that worried her. The only people who came down to the morgue were usually dead or in search of something, and either way she always knew how to help; but some part of her knew she should make more of an effort to connect with the people around her.

Lately, though, she'd been spending so much time down here that she was beginning to become slightly too comfortable with it. Even Jane usually called or texted before she came down, which meant that Maura was unlikely to be disturbed. She'd taken advantage of this by talking out loud – sometimes to herself, sometimes to the bodies she was examining. It helped her to think, and it made the morgue feel just a little less cold.

"You know," she was telling the victim, who'd been identified as Victoria Langley, "you're the third person who's shown up like this in the space of two weeks." She paused, her scalpel over the woman's sternum. There was something about the letter on her chest that hit home, although Maura couldn't figure out what it was. "Jane thinks it's a serial killer," she went on, starting the autopsy. "She could be right, of course, but why don't we just open you up first and -"

"You know," said an amused voice in the doorway, "you should really buy her dinner first."

Maura pointedly ignored Jane and carried on with her autopsy. In a moment she felt the detective come up behind her, looking over her shoulder – an irritating habit she'd developed lately, but Maura hadn't had the heart to ask her to stop.

"I'm sure she doesn't mind," Maura murmured, her attention fixed on what she was doing. Jane still stood behind her, but she didn't say anything for a long time. Eventually Maura turned to face her, narrowing her eyes slightly. "You're hovering."

"I'm not hovering," Jane said indignantly, but Maura only had to raise her eyebrows for the detective to give up on the ruse. "I'm worried about you," she said bluntly, catching Maura by complete surprise.

"And I'm worried we're not going to find this woman's killer," Maura countered, gesturing at the girl lying on her autopsy table. This time it was Jane's turn to raise her eyebrows, and Maura relented. "For what it's worth, I'm fine," she said, returning to the body. She was almost finished with the autopsy, which was just as well because she had a feeling that Jane wouldn't leave until she gave her something useful. "And I don't know why you'd think otherwise."

Too late, she realized the opening she'd given Jane.

"You were off at the crime scene, and for that matter you've been acting weird for weeks," Jane said promptly, her attention switching almost entirely from the case to Maura. It was a wonder anything got done around here, given how easily Jane could be side-tracked; but then again, once she got an idea in her head she couldn't be dissuaded, and she was single-minded when it came down to tracking down a perp.

"Off?" Maura repeated, closing up Victoria and then pulling off her gloves. "Off what?"

She knew perfectly well what Jane had meant, but she also knew that she didn't want to talk about this. She threw her gloves out and walked over to her computer, hoping Jane would get the hint and leave her alone. But the detective just trailed after her, evidently not ready to give up on this train of thought.

"You know what I mean," Jane said, crossing her arms. She paused, and when she spoke again her voice was softer, almost sympathetic. "You didn't seem like yourself at the crime scene today."

"Of course I was myself," Maura said, trying to keep her voice light, "who else would I be?"

Jane's expression made it clear that she didn't think it was funny. And suddenly Maura had the urge to tell her friend everything, although she didn't know why. It's not like there was even really anything to _tell_ her anyway. It was simply a reaction to prolonged stress and anxiety – and she was the only one who could deal with those. She'd long since grown used to doing things alone, and after everything that had happened recently she didn't feel like she should burden her friends with her petty problems.

"Spill," Jane said sharply, and Maura glanced down at the floor, wondering what she'd spilled. Then she realized what Jane had meant and looked back up at her, embarrassed. "Tell me what's going on," Jane pressed.

Maura tried to turn her attention back to the computer again but Jane reached out and closed the laptop, forcing Maura to look at her. Finally, Maura crumbled. "It's nothing serious," she said. "I've just been having trouble sleeping lately."

Jane's expression softened again, her eyes filled with concern. "What do you mean?"

 _I'm having nightmares,_ Maura wanted to say, _about Hoyt. About what he did to you. In the dreams, I can't save you. And sometimes -_ She shook her head. "I have this recurring nightmare," she said, praying Jane wouldn't take it any further. Maura was almost pathologically incapable of lying, but she didn't want to tell her friend about the dreams. If Jane knew how worried Maura really was, she'd only get protective and worried herself – and Maura couldn't do that to her.

As if in answer to her prayers, the morgue door swung open and Frankie walked in. He balked a little as he picked up on the tension in the air, but Maura and Jane both made an effort to pull themselves out of the conversation and dispel some of the tension.

"Do we have anything yet?" he asked, sounding slightly nervous.

Maura smiled at him, letting him know that he wasn't really interrupting anything. "As I was just telling Jane," she said, deliberately avoiding Jane's surprised gaze, "everything I've found is consistent with the first two victims."

Jane and Frankie shared a look, each silently processing what that meant. "So if the same person killed all three of them…" Frankie began, and Jane nodded.

Maura noticed that Jane's hand drifted down to her gun, holstered at her side, and the movement was enough for the scar on her palm to become visible. The doctor turned away, not wanting to get caught up in thoughts like the ones that were pushing at the edges of her mind.

"This is the third victim," Jane said heavily, her hand still resting on her gun. She shared a significant look with the others, and then looked at Victoria's body. "Which means we have a serial killer on our hands."

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 **Annd, there's the first chapter. Please do fave/follow/ review, and I hope to see you all soon for the next chapter.**


	2. Chapter 2

***quietly slinks in, mumbles an apology, and leaves a chapter behind***

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 _"There will be killing till the score is paid."  
_ _― Homer, The Odyssey_

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"Have you seen this?"

Jane jerked her head up at the voice to see Korsak standing in front of her desk and brandishing a copy of the morning paper.

"Good morning to you too," she said drily, and Korsak responded by slapping the paper down on her desk so that she could read the headline, nearly knocking her coffee over in the process. She snatched her cup up and started to say something mock-scathing, but then she caught sight of the headline.

 _The Doctor Is In: Does Boston Have A New Serial Killer?_

" _Crap_ ," Jane muttered, skimming the article. Not only did it refer to the new killer as 'a lunatic prowling the streets of South Boston', it also implied that BPD was ill-equipped to handle it and even suggested that the victim count could rise to be high enough to rival Hoyt's, whose confirmed kills numbered in the twenties. "There have only been three murders," Jane pointed out, frustrated; she knew that wouldn't mean a thing to the press. If they could stir this up and make it seem like another deranged psychopath was on the loose, they'd probably at least double their ratings – and cause city-wide panic in the process.

"This is bad," Korsak agreed, leaving the paper and going to his desk. He sat down heavily, as if the thought of the oncoming media frenzy was physically exhausting already.

"You all right?" Jane asked, noticing the stiff way he was moving – that was more than mental exhaustion or simple stress.

"I'm just not as young as I used to be," Korsak said, sounding weary but like he was doing his best to be cheerful.

Jane let the matter rest, knowing that if something was bothering him he'd tell her sooner or later – and probably sooner if she didn't push it. It had been a little under a week since the last murder, and so far they'd done a good job keeping it under wraps. But the investigation was dragging on and they still didn't have any suspects, and it had only been a matter of time before the media caught wind of this. She didn't miss the allusion in the serial killer's title, and wondered if it had been a deliberate sleight to her – naming the new serial killer after the old one who had nearly killed her several times. The dawn of The Surgeon was gone; The Doctor was in charge now.

"Do you and Dr Isles have another big night planned tonight?" Korsak asked, an obvious attempt to lighten the mood.

Jane groaned. "God, I hope not," she said. Last Friday – the day before the murder – Maura had insisted that she come to The Dirty Robber with her, and had then consumed more wine than was probably good for her. Jane had left at around midnight, tired of fending off the sleazy guys who kept offering to buy her drinks, but Maura had stayed to catch up with an old med school buddy of hers. As far as Jane knew, Maura hadn't made it home until after two – and had still somehow managed to show up for work looking like a supermodel, whereas Jane had felt like a zombie and probably looked even worse.

Korsak laughed. "Just be glad Maura's not a people person," he said.

"Oh, she is," Jane said, amused. "Just as long as those people are dead."

Although her words may have seemed harsh, they were all in good fun; she'd have said them to Maura's face if she'd been here. At that moment she got a message from Maura herself, and was out of her chair before she finished reading it.

"Maura's got something," she said, already heading for the door.

"Let's hope it's something useful," Korsak said, retrieving the paper from Jane's desk and glaring at the headline as if it had personally offended him. "I don't know how long we can mitigate this."

Jane waved over her shoulder at him in acknowledgement as she slipped out the door, and then she headed for the morgue. God, she hoped Maura had something, because if not they were no closer to finding the serial killer – and the killer was probably closer to making their next move.

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This time Maura was prepared for Jane's arrival, although she wasn't prepared for this conversation.

"What've you got?" Jane said without preamble, and Maura was reminded of the first case they'd worked together. It had taken at least twice as long as it should have because she and Jane had been at odds the whole time. Jane's brusque manner had thrown her, and it had taken longer than it should have for Maura to see through that and realize what a good person the detective really was. Which is why she had to do this.

"Close the door," Maura instructed, and Jane balked, not used to being given such direct orders from her friend and colleague. Realizing how harsh she'd sounded, Maura added in a softer tone, "Please."

Still taken aback, Jane did as suggested and then turned to Maura, her expression puzzled. "What's going on?" the detective asked, and Maura noticed that she was fiddling again. Whenever they were working a particularly stressful case, Jane would fall back into a nervous habit – pressing the thumb and forefinger of one hand against either side of her palm, rubbing the old scars. She probably didn't realize that anyone noticed; and in her defense, no one aside from Maura probably did.

"This is difficult for me to say," Maura said hesitantly. She'd rehearsed this conversation a hundred times, but here she was, two lines into it and backing out already. Steeling herself, she said, "You must have noticed the similarities."

"Similarities?" Jane echoed. She seemed confused for a second, and then it clicked. She crossed her arms, a defensive gesture. "You mean between this serial killer and the last one?"

"Yes." Maura tried to keep her voice steady, but she hated talking about this. She knew the nightmare Jane had gone through with Hoyt, and she didn't want to cause her any more pain. But this was important. "The MO is similar. Not the same, but alike enough to cause some concern."

"What kind of concern, Maura?" Jane's voice was level but her eyes were flashing, a sure sign that this conversation was hitting close to home.

"Look at this," she said, grabbing two files from her desk and then walking over to an empty morgue table, her heels clicking on the floor as she did so. Jane followed warily, watching as Maura spread out an array of pictures on the table. "These lacerations," she said, pointing to a couple of the pictures, the ones showing the throats of several victims, "they're all the same. Very precise. Almost… almost professional."

Jane's eyes darted across the table as she tried to fill in the blanks.

"Are you saying that The Doctor could be an actual medical professional?" she asked finally, looking at the two sets of images – Hoyt's victims and the victims of the latest killer.

"It's possible," Maura said, the closest to a definite she would be willing to give. She started to say something else, but cut herself off.

Jane moved away from the table, leaning against the nearest counter. Her expression was troubled, and her silence troubled Maura even more.

"It's unlikely that it's Hoyt," Maura offered, but she could tell her words upset Jane nonetheless.

"I checked with Korsak," Jane said absently. "He said Hoyt's still on lockdown. It's not him."

Maura breathed out slowly, trying to find the words to comfort Jane. But she'd never quite found the right thing to say, even with all the unwelcome practice. Hoyt had gone after Jane several times now, and each time Maura felt like he'd taken a little bit more of the detective when he left. Each time it was like her edges got sharper, her guard a little stronger, her eyes a little darker. Maura normally wasn't one to think in such emotional terms, but it was the only thing that seemed to suit the situation – none of the scientific explanations meant anything when she saw the haunted look in her best friend's eyes.

"It's not Hoyt," Jane said again, less abstract and more thoughtful now. Her expression turned even more grim. "But it might be the next best thing."

She met Maura's gaze, and the doctor felt her heart constrict. She'd seen that look in Jane's eyes before, more often than she liked. It was a look of determination, of fear, of dawning realization.

Jane started fidgeting again, rubbing her right hand with her left, her fingers running across the scars and her eyes darkening. "I think my old friend Hoyt has a new apprentice."

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By Saturday Jane was jumping at every noise; by Sunday she was having nightmares again; by Monday she was afraid she was losing her mind.

It was like this every time Hoyt's memory resurfaced, every time she saw a road flare or a scalpel or even a body bag. It was like this every time, except this time it was worse. She woke up on Monday night in a cold sweat, convinced that Hoyt had been in her apartment. But it had just been her and Jo Friday, who had jumped up onto her bed and pressed her nose into Jane's hand in a silent gesture of comfort. Jane ran her hand through Jo's fur, breathing hard and trying to keep herself away from the edge of panic.

She'd been here so many times before, but it always caught her by surprise. She'd dealt with psychopaths before, with serial killers and rapists and more criminally insane people than she could count on both hands. But Hoyt was different. He wasn't the only one to hurt her, but he was the only one who had ever made her feel like a victim. She still saw his face in her dreams, still felt his breath on her neck, still remembered the feel of the scalpel gliding across her neck. And she hated herself for letting it get to her.

It was almost three am, and for a while this thought stopped her from reaching out. She didn't feel safe alone, but she didn't want to wake anyone else up. It wasn't like she was in any immediate danger anyway – The Doctor hadn't made any threats against her, hadn't made any indication that they were affiliated with The Surgeon, much less on the same mission. She hadn't even told the others about her theory; there was no sense in worrying them until she was sure this had something to do with Hoyt. She knew how protective Korsak and Frost would be over her, and how much it would worry Frankie, and she couldn't do that to them.

But when she was still awake at four, she realized that she couldn't spend the rest of the night alone. Trying to convince herself that there was no weakness in reaching out to a friend, she dialled Maura's number and waited. And waited. She called twice more and there was no answer, and after sending a text for good measure she lay back down, feeling strangely disappointed. Maura had never let her down before, and although Jane knew she couldn't blame her for not answering, she was still almost hurt.

It was almost five when she fell asleep, phone in hand and Jo Friday curled up beside her, and for once her sleep was blissfully dreamless.

X.X.X.X.X

On Tuesday morning Maura was woken by banging on the door. She opened her eyes blearily, silently hoping that whoever was trying to break down her door would just do it quietly and rob her already so she could go back to sleep. But when the person started shouting her name she realized what it was and quickly slipped out of bed, trying to push the remnants of her bad dreams from the edges of her mind. She'd slept badly, but she was used to that by now; this case had stirred up old feelings and fears and she hadn't quite worked out how to deal with them yet.

Maura opened the door to see an irate Jane Rizzoli standing on her doorstep, and the look in Jane's eyes made Maura want to close the door again as fast as she could.

"Where the hell have you been?" Jane asked, her tone making it clear that _Sleeping_ would not be an acceptable answer.

"I was…" Maura frowned, noting that Jane was fully dressed – and in her work clothes, not her street clothes or her jogging clothes. She stepped back to let Jane in, but the detective didn't move. Maura's frown deepened. "What's going on?"

"It's good to know it's not just me you're ignoring," Jane said. "Do you even answer your phone anymore?"

"Of course I do," Maura said, but once she'd retrieved it from her nightstand she realized what the problem was. "I always answer my phone," she said faintly when she came back to the door, "except when I turn it off."

Jane stared at her, equal parts incredulous and furious. "We're in the middle of a homicide investigation and you _turn your phone off_?"

At first Maura couldn't understand why Jane was so angry, but then it hit her. Jane had been worried. They'd learned from experience that if anyone on the team didn't answer their phone, they were likely in trouble. And with a Hoyt-like killer on the loose, now was no time to be dropping out of contact. "I'm sorry, Jane," she said, and she meant it. She paused. "Is that why you're here?"

"Actually, no." Jane brushed past Maura, not waiting for an invitation, and once she was past the threshold she turned to face her friend. "Get dressed. You have five minutes."

Maura stared at her. "What's going on?"

Jane grimaced. "We've got another body."

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 **R &R guys, and I'll see you all next time.**


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